1,721,135 research outputs found
A comparative study of the industrial exploitation methods for stone slabs in Italian quarries
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Effect of water nanoconfinement on the dynamic properties of paramagnetic colloidal complexes
Full text linkThe anomalous behavior of confined water at the nanoscale has remarkable implications in a number of nanotechnological applications. In this work, we analyze the effect of water self-diffusion on the dynamic properties of a solvated gadolinium-based paramagnetic complex, typically used for contrast enhancement in magnetic resonance imaging. In particular, we examine the effect of silica-based nanostructures on water behavior in the proximity of the paramagnetic complex via atomistic simulations, and interpret the resulting tumbling dynamics in the light of the local solvent modification based on the Lipari-Szabo formalism and of the fractional Stokes-Einstein relation. It is found that the local water confinement induces an increased "stiffness" on the outer sphere of the paramagnetic complex, which eventually reduces its tumbling properties. These model predictions are found to explain well the relaxivity enhancement observed experimentally by confining paramagnetic complexes into porous nanoconstructs, and thus offer mechanistic guidelines to design improved contrast agents for imaging applications
Nano-metering of Solvated Biomolecules Or Nanoparticles from Water Self-Diffusivity in Bio-inspired Nanopores
Full text linkTaking inspiration from the structure of diatom algae frustules and motivated by the need for new detecting strategies for emerging nanopollutants in water, we analyze the potential of nanoporous silica tablets as metering devices for the concentration of biomolecules or nanoparticles in water. The concept relies on the different diffusion behavior that water molecules exhibit in bulk and nanoconfined conditions, e.g., in nanopores. In this latter situation, the self-diffusion coefficient of water reduces according to the geometry and surface properties of the pore and to the concentration of suspended biomolecules or nanoparticles in the pore, as extensively demonstrated in a previous study. Thus, for a given pore-liquid system, the self-diffusivity of water in nanopores filled with biomolecules or nanoparticles provides an indirect measure of their concentration. Using molecular dynamics and previous results from the literature, we demonstrate the correlation between the self-diffusion coefficient of water in silica nanopores and the concentration of proteins or nanoparticles contained therein. Finally, we estimate the time required for the nanoparticles to fill the nanopores, in order to assess the practical feasibility of the overall nano-metering protocol. Results show that the proposed approach may represent an alternative method for assessing the concentration of some classes of nanopollutants or biomolecules in water
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
New method to compute mixed water and electrolyte changes in hyponatremia: a preliminary report
No full textShock propagation effects in multilayer assembly including a liquid phase
No full textDuring a ballistic impact, the protective material that plays the role of armour has to dissipate the kinetic energy in order to limit the projectile penetration in the target. Our aim is to emphasis on the role played by a liquid-filled system on the impact energy mitigation due to cavitation inception and later bubble expansion. To observe this, small scale experiments have been carried out on a three layers sample (Aluminium-Water-PMMA) submitted to shock waves induced by laser impact applied on the Al face. Rapid camera visualizations allow reproducing, at small scale, the effects of projectiles on armours for various monitored impact energies. We observe the formation of bubbles for sufficiently intense impacts due to traction effects in the water caused by the multiple reflections of waves within the sample. The cavitation threshold of water under dynamic loading is then experimentally investigated for two samples: one with 600 μm thick Al / 400 μm of water and 3 mm of PMMA, the other with 1000 μm thick Al / 1600 μm of water and 3 mm of PMMA. Using dimensional analysis, we show that the energy taken during the process of inception and bubble expansion becomes more important as the energy of the impact increases
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